I am in a very hierarchical organisation (Units -> Sectors -> Offices), and it would be very handy if I could specify that, for example, an office-level-group consists of a couple of members + its sector-level-group-equivalent.

example:
InternetOfficeAdmins =

{User1, User2, WebSectorAdmins}

WebSectorAdmins =

{UserN, ITUnitAdmins}

ITUnitAdmins =

{Userx, UserY}

This way, I would not need to add UserX to all three groups (or add all three groups to each project)